The present invention relates to new resins which are grafted polyethylenes or grafted ethylene copolymers and which are thermoplastic or, where appropriate, cross-linkable and soluble at ambient temperature in organic solvents and/or aqueous media.
The invention also relates to a process for preparing these resins and to their application as binders for coating, especially in paints, varnishes and inks.
Grafted ethylene poly- and copolymers are now well known. They have properties which are modified but which remain close to those of the original ethyene poly- and copolymer, the grafting being sed, above all, to modify certain specific characteristics such as dyeability and improvement in adhesion. They are, in fact, thermoplastic and insoluble at ambient temperature in the usual organic solvents such as hydrocarbons, alcohols, esters, ethers and ketones.
Various methods of manufacturing these grafted ethylene poly- and copolymers are known.
According to a first method, sheets of polyethylene brought into contact with monomers by themselves or in solution are subjected to high-energy radiations such as .alpha. or .gamma. rays or an electron bombardment. Sheets of polyethylene with modified surface properties are obtained. The formation of homopolymers in the solution is also observed.
According to a second method, described in European Application No. 100,912, the grafting operation is carried out on polyethylene in a molten state in the presence of styrene and of free radical initiators, and, if desired, an organic solvent. In parallel with the formation of homopolymers, modified polyethylenes exhibiting excellent adhesiveness and used as adhesives on polyolefins are obtained. These modified polyethylenes are not soluble in organic solvents at ambient temperature.